N'DJAMENA, Chad -- Fighting in Chad could trigger a humanitarian crisis in neighboring Cameroon, particularly for children, Save the Children warned Monday.

"In a situation where a lot of people are fleeing, it is very likely that children will be separated from their parents," Gareth Owen, Britain's Save the Children's director of emergencies, said in a statement. "We don't know what conditions the people crossing into Cameroon will be facing and we are very concerned that children will be alone and in danger."

Fighting in Chad's capital of N'Djamena forced large numbers of people to flee across the bridge into northern Cameroon. Owen said aid work also is threatened as violence disrupts movement of people and supplies.

While thousands flee Chad's capital, the United Nations said thousands of refugees trying to escape attacks in Darfur streamed into Chad, The New York Times reported Monday.

The rebel group controlling the part of Darfur under attack warned the U.N.-AU peacekeeping force not to enter the area because it was an active war zone.

"There is no cease-fire, the war is going on," Suleiman Sandal Haggar, a Justice and Equality Movement senior commander, told the Times in a phone interview.